Process for purification of used lubricating oils



Registered July 26, 1938 PROCESS FOR PURIFICATION OF USED LUBRICATING OILS Adolfo Silenzi de Stagni, Buenos Aires, Argentina,

N o Drawing.

Application May 8, 1936, Serial 1 Claim. (01. 196-16) This invention relates to the utilization of a means for application to oils, greases or such lubricants as may have, been used as such and in which it is made possible by this means to cause precipitation of all their impurities.

The said means performs within the lubricant to which it is applied a catalyzing, anti-emulsionizing, neutralizing and reconstructing action.

The means in question is composed of a sodium or potassium silicate (water-glass) solution or of a solution in which both are combined, this solution having a particular composition, being obtained from the pure solvent and bringing about special effects when employed for purifying and regenerating greases, oils and used lubricants.

I said that the sodium or potassium silicate has a particular composition since it is not possible to obtain the said purifying and regenerating results in used lubricants by employing such commercial silicates as are generally used in industry and the silicic anhydride contents of which is in the neighbourhood of 48102.

Preferably, the product intended to perform the function of a medium in this case of novel applica tion should correspond with such alkaline silicates as are obtained pure in the natural condition, and not with those obtained in an artificial manner, by departing from neutral silicates to which a proportional quantity of sodium hydrox-- ide (NaOH) or potassium hydroxide (KOH) was added. It is peremptory to establish this distinction. for the majority of silicates plants resort to this recourse when receiving special orders for alkaline silicates having a particular composition, obtaining in this manner the chemical In practice it has been found that there is a fundamental difference in the use of a pure solvent from the use of an artificial one, that is to say, between an original alkaline silicate and a neutral one which was caused to acquire an alkaline reaction by means of sodium or potassium hydroxide, by putting in solution a higher number of OH ions. Notwithstanding the fact that equimolecular solutions of one and the same base are concerned in which the density of the same is increased by the m-olecular weight of the dissolved salt, it has been found that this addictive character of density obtained by this third dissolved body leads to different individual characteristics. As a matter of fact, pure alkaline silicates when brought up to a particular density by aqueous solutions become dissociated in respect of their ions, and this electrolytic dissociation interferes also with the individual characteristics, giving rise to different and complex reactions, energies and phenomena which also-exercise a different tity of free ions.

to distinguish them from those which in current 'Vent by means of a quantity of adsorbed water.

,upon the mixture is stirred for some minutes or the bottom within a shorter or longer time, de-

osmotic pressure closely dependent on the quan- This distinction between the two products constitutes one of the greatest merits of the invention, and the foregoing explanation is to a certainlpoint necessary for explaining that in referring hereinafter to the density of a pure alkaline silicate the same is meant to be the maximum to which this may be brought up to with regard to its original chemical composi-- tion and constitution, and that it is not due to any concentration, dilution or-substances added to other silicates of a different nature. r

In the course of this description I will refer to alkaline silicates of a special composition so as and generic use are known by the name of sodium or potassium silicates or water-glass, usually employed in the various industries and which answer to the standard composition Na2O, 4Si02, or K20, 4SiOz, which has the same applications; and I will particularly refer to sodium silicates since they are the most usual, the cheapest and the most easy of access. Of these it is recommended to preferably employ such as have a composition oscillating between NazO, 2.6Si02 and 'NazO, 3Si02, e. g., a medium composition of NazO, 2.6SiO2, this original silicate of medium alkalinity having a theoretical density of 53 B., which in practice comes down to 48-50 B. This difference is due to residues always left over in the manufacturing furnaces by other silicates having a different composition. Thus, where reference is had to a medium composition of 2.6Si02 allowance for certain elasticity limits should be made not only in density but also in composition which might vary as between 2.5 and 2.78102. The silicates to be used in accordance with this invention should be brought up to a density of .solution of from 38 to 42 B., obtained from the pure sol- The solution is admixed with the product it is intended to regenerate in the proportion of from 5 to 10% or even more, depending on the lower or higher degree of impurities contained in the greases, oils or lubricants to be treated, wherethe time necessary, and allowed to stand, there- 7 after, in perfect repose. The said alkalinesilicat'e stances, finely subdivided in the oily mass and which will dissociate themselves, settling down at pending on the quantity of foreign matter contained, on the colloidal degree of the same, on

the surrounding temperature and on the physical influences of each product treated. By the dissociation of these solid or liquid pseudo-solutions or suspensions, the impurities settle down on the bottom of the vessel, in conjunction with the alkaline silicate, the grease, oil or lubricant which has been treated being thus perfectly purified and regenerated and capable of being discharged through lateralorifices or by means of syphon devices, special funnels, pipettes, sucking'bottles, or in any other suitable manner. The used greases, oils or lubricants exposed to this purifying and regenerating treatment recover their original characteristics of smell, colour, density, flash point, combustion point, congelation viscosity, lubricating power and purity, none of these properties being obtained by employing either other processes or other commercial neutral sill-- cates having a composition of 48102 in silicic anhydride, the molecular weight of the silicic anhy ance with this invention which tends to destroy this physical equilibrium which keeps the impuritiesaway from the action of gravity. In theapplication of the process, by employing as the purifying and regenerating .agent the silicate types mentioned above and which exercise a suitable.

catalyzing and anti-emulsionizing action, as soon as they have been mixed and stirred with the already used greases, oils and lubricants in general such minute oil drops as enclose 'theirnpuri ties are obliged to widen and to get together, and owing to'the increase in their surfacetension a change in the physical condition is brought about which destroys the stableness, dissociating the emulsified impurities and causing thus .all'of the stabilizing colloidal substances to slowlyprecipitate down onto the bottom of the vessel, due to their greater specific weight. A like behaviour will be shown by the water so often obtaining,-

in a condition of emulsion, in already used greases, oils and lubricants in general, which water the alkaline silicate did not succeed in adsorbing and which is present in general in a proportion of from 0.5 to 2%,having its origin in the condensa .tion of the aqueous vapour produced by the cylintiers of such machines and mechanical pieces as work at high speeds running hot. Also such mucilaginous substances and other heterogeneous liquids as may be present in emulsion, if not soluble among one another will settle separately in accordance with their different density. Another and not lesser advantage of the application of this process by means of. the said silicates resides in that it is feasible thereby to purify and regenerate high viscosity products as well asto correct those having some excess of acidity by way of fatty or free acid, a thing so frequent in oils and lubri- 'cants which have undergone a deficient refining and which is being acquired also by use. In these cases the treatment with the said alkaline antiemulsionizing agent, in addition to giving them back their original properties, produces a practi- -cally neutral reaction.

To sum up, this invention is characterizedin that it employs. as the purifying and regenerating agent of such greases, .oils of whatever body or viscosity and lubricants in general that have been used already a new catalyzing, anti-emulsionizing and neutralizing product constituted by sodium or potassium silicates (water-glass) or by both, having a composition which is comprised within Na2O,2SiO2 and Na2O,3SiO2 or K2O, 2Si02' and Practical experiences have shown that alkaline silicates in general, and particularly those of sodium having. a composition comprised within Na2O,2SiO2 and Na2O,3SiOz present hitherto un known biological phenomena, and that in solutions. of a, certainidensity they have different properties andeffects, specially in purifying and regenerating already used greases, oils and lubricants in general. This new aspect constitutes a novel discovery in the technical field, explainable to a certain extent if we consider that alkaline silicates are little known and that the only ones well defined at presentare: sodium metasilicate NaasiOa and potassium metasilicate K2,SiO3.

As a matter of fact, the investigations made have shown that some alkaline silicates and in particular those of sodium comprised withinthe indicated composition this invention is dwelling on have a special behaviour and permit to integrally re-establish the 'molecular building of greases, oils and lubricants in general exhausted by use and which, due to the energetic polymerizing actions of the said. catalytic-agents, is reconstructed and caused to again gather together one with another the molecules of the products treated which might present free ligaments. .It has been found also that the said silicates present complex and unknown polarimetric phenomena leading to results and values distinct from those i,

of the commercial silicatesusually' employed.

To prove what I have set out just now'I shall by way of example mention two results obtained in regenerating a mixture of various used motor car oils. Result No. l, was obtained with. a

Na2O,2SiO2 and NazOBSiOz, anclNo. 2 with a sili- .40 sodium silicate havinga composition as between cate whose silicic anhydride contents was higher than 3Si02. The used oil on which the trials were realized showed the following characteristics:

The low flash point indicated revealed the dilution of other light hydrocarbons which was evidenced by a smell the lubricant emitted, Conse- Density at 15 0 0.925s Viscosity Engler at 25 C -4. 28.26 Viscosity Engler at 50 C 7.00 Viscosity Engler at C. 2.81 Viscosity Engler at C 1.57 Flashrpoint (open'Marcusson vessel 5 C. i

per minute) 69 C. Combustion point 1 143C Minimum temperature of fluidity 14C. Acidity in em 0.023% Moisture 'j traces quently, it was submitted to a distillation trial which gave the following result:

Distillation Engler First drop C.

Up to C. it distilled 2% by volume Up to, C. it distilled 3%fby volume Up to 200C. it distilled 4% by volume Up to 225 C. it distilled 5.5% by volume Up to 250 C. it distilled 7.5% by volume Up to 275 0; it disuliednrrni; 8% by volume Up to 300. 0. a distilled 9% by volume .Up to 350 C. it distilled 11% by volume Up to 375 C. it distill-ed 13% by volume In order to eliminatethe naphtha and kerosene 1:.

contents the lubricant was distilled up to 320 C. before undertaking the trials on the sample referred to. Thereafter, the regeneration treatment was proceeded to, the two sodium silicate types mentioned being used separately, with both trials being realized under strictly the same conditions.

As will be appreciated, the result obtained with the sodium silicate No. 1 answers tothe characteristics of a semi-dense lubricant and may be considered as highly satisfactory, which cannot be said of the trial made with silicate No. 2, for it indicates deficient characteristics which do not comply with the requisites specified for such oils as are used for the internal lubrication (cylinders, pistons and other movable parts) ofexplosion motors for motor cars, trucks, motor launches,

tractors, winches, etc.

I wish to point out that in applying the described treatment to light oils of a low specific Weight (for instance, transformer insulating oils) it should be taken into account that the silicate decants with a certain rapidity. In this case, in addition to bringing the latter up to a lesser and proportional density of solution, it is advisable to from time to time stir the treated oil or repeat the treatment so that the alkaline silicate may remain in touch with the oily mass as long as possible. This applies also to such greases, oils and lubricants in general as possess a high degree of acidity.

The new regenerating means described also proves at first sight to be more practical and cheaper as compared with the processes hitherto employed and known, including mechanical means such as filtration, centrifugal action, etc., which, on the other hand, scarcely permit to attain a satisfactory result since they do not succeed in developing the physical effort necessary for the perfect elimination of the colloidal impurities.

It is possible, however, to remedy this drawback by combining said apparatus with the de-.

scribed treatment in which case it will not be necessary to wait for the complete decantation of the dissociated impurities, the treated products being transferred to the filtering and centrifugal machinery. It is obvious that as soon as the physical equilibrium condition of the emulsions and suspensions is destroyed the aforementioned drawbacks due to insufficiency of the centrifugal action will actually disappear, and it will be possible then to afterwards utilize with satisfactory and perfect results any type and class of centrifugal apparatus known in industry, for as a con sequence of the dissociation of the impurities an enormous decrease is attained in the physical effort necessary for the extrusion of the emulsionizing'colloidal substances which thus prove to be settled out and partially accumulated in the form of a very fine sludge.

The invention is quite obvious from the foregoing description and does not need any further explanation for those acquainted with the art.

It is quite clear. that various modifications may be introduced in the manner of using and applying the alkaline silicates referred to without thereby departing from the scope of the present invention which is clearly described and ascertained in the appended claiming clause.

What I claim is:

A process for purification of used lubricating materials comprising mixing such material with an aqueous solution of sodium silicate of a composition lying between' Na2O:2SiO2 and Na2O:3SiO2 and having a density of from 38 to 42 B., and permitting the mixture to stand until the purified oil rises above the water and the impurities separate from the oil and are taken up by the water.

A. SILENZI DE STAGNI. 

